Jet fuels or diesel fuels that are clean and contain substantially no sulfur, nitrogen, or aromatics are expected to be on the verge of a dramatic increase in demand, for example to meet the pressing need of automobile manufacturers for a global standard. See the testimony to the U.S. Congress of Oct. 5, 1999 by James A. Spearot, Director, Chemical and Environmental Sciences Laboratory, General Motors, on behalf of the Partnership for a New Generation of Vehicles Advanced Fuels Group. However there are substantial unsolved technical problems connected with such a development.
Recently developed fuel compositions are cleaner burning, but are seriously deficient in certain fuel-desirable technical attributes. These attributes are apparently lost with the removal of sulfur and/or nitrogen. Accordingly there is a newly emergent need, and corresponding thereto, a significant technical problem to be solved of how to secure improved clean jet or diesel fuel which more effectively compensates for removal of sulfur and/or nitrogen and/or aromatics, especially for removal of sulfur.
Such novel fuels would comply with increasingly stringent regulatory standards, and would be highly sought after by the consumer both for improved environmental acceptability and for lack of compromise in terms of effectiveness. This would be especially true for fuel system lubrication of injectors and fuel pumps in modern engines.
Another growing need in the field of low sulfur jet/diesel fuels (including in general sulfur-free types) is the need for a common or “fungible”, i.e., economically interchangeable, fuel/additive or fuel additive “concentrate”. Such commonality would permit a relatively small number of specialized plants, such as FISCHER-TROPSCH plants, to serve as a source of supply of a “concentrate” which could be blended in any petroleum refinery with all manner of jet/diesel fuels, especially low-sulfur fuels, including hydrodesulfurized and/or biodesulfurized conventional petroleum fuels as well as FISCHER-TROPSCH derived fuels. Thus the benefit of the additive would be spread over all the principal ultra-low sulfur jet/diesel fuels, and solve for all of them the problems incurred by sulfur-removal. Such a benefit could indeed be material to the protection of the entire base of investment in conventional petroleum refining. Moreover, if the additive were to be a concentrate, the above need would be addressed much more viably and economically.
Unfortunately, known processes for making fuel lubricating additives of the relatively long-chain type required are subject to intrinsically producing too low a level of useful additive, diluted by hydrocarbons which are uneconomical to transport or to remove. Moreover, there is significant room for improvement in the properties of such additives.
Known processes for example include those which produce so called “native” alcohols in a FISCHER-TROPSCH derived fuel. Moreover, the total amount of such “native” alcohols is insufficient when blending to high dilution for modern jet/diesel fuel lubrication. The levels of the native alcohols produced by the FISCHER-TROPSCH processes are inadequate in providing lubricity necessary in modern jet/diesel fuel concentrates or blendstocks. The type and level of branching in the native alcohol is limited; they are mostly linear. Further, in products of such processes, there is no independent variability of branching/heavy atom count in the alcohol as compared to the co-present fuel hydrocarbons, thus no possibility of concurrently optimizing (a) lubricity properties and (b) other important parameters, e.g., cetane number or smoke point. In other words, known process always have the heavy atom count for hydrocarbon equal to the sum of carbon atoms and the heavy atom count for alcohol equal to the sum of carbon and oxygen atoms.
Conventional non-alcohol approaches to additives for low sulfur fuels have been tried and found wanting. State of the art, for example, is represented by WO 96/25473; WO 98/21293; WO 98/28383; WO 99/00467; and U.S. Pat. No. 5,488,191. Such additives have one or more important disadvantages, for example they contain nitrogen, aromatic rings, have overly high molecular weight, or are relatively uneconomical.
Particularly desirable, then, would be a common, concentrated, biodegradable, economical additive which is more lubricious. Ideally, such an additive would be dramatically lower melting than any known additive currently available on commercial scale in concentrate form. Moreover, such a particularly desirable additive would be free from disadvantages such as excessively high molecular weight, and would completely and cleanly combust without any difficulty. Compositions comprising such an additive would permit independent control of the structure of the alcohol derivatives and the structure of the fuel hydrocarbons, for an overall optimization of the fuel properties of mixtures containing both.
Accordingly, it is an object of the present invention to secure such a concentrated additive, derivative low-sulfur- or zero-sulfur-fuels containing it, and processes for making it.
Processes for making jet and/or diesel fuels have been markedly improved in recent years. Such processes include deep hydroprocessing of crudes as well as recently improved FISCHER-TROPSCH slurry bed reactions to convert synthesis gas (syngas) to a wax, followed by hydrocracking/hydroisomerization and distillation to separate the desired fuel streams. The products can be optimized around jet/diesel.
The present invention substantially modifies such processes and compositions, affords novel fuel compositions, including the desired concentrated additive, and solves the aforementioned technical problems.
Compositions of the present invention have numerous advantages, for example in permitting a much greater flexibility for the formulator in producing finished fuels, or concentrated additive blendstocks which are clean, highly biodegradable, have superior lubrication properties, and that can be pipelined or shipped as liquids under ambient or even arctic temperatures (e.g., −35° C. (−30° F.) or even lower).
The inventive fuels and processes permit independent optimization of the properties of fuel hydrocarbons and alcohol derivatives for overall superior results.
An especially important advantage is that the concentrated additives or “concentrates” of the invention separate much less readily from diluted blendstocks and/or finished fuels at low temperatures. This makes them highly desirable in a number of critical applications, including for use in jet fuel. Further, in preferred embodiments, the compositions are substantially olefin-free and C1-C9 carboxylate-free, thereby essentially eliminating peroxide forming tendencies and reducing corrosion/gum formation.
The present invention is accompanied by advantages useful not only to the manufacturers and consumers of fuels, but also to manufacturers and consumers of detergents, for example in that, by promoting the manufacture of selected alcohol derivatives for fuel uses, important economies of scale will make similar alcohol derivatives and/or sources of such derivatives (i.e., alcohols) much more affordable for detergent uses.
The present invention has numerous advantages. It allows transportation of concentrates as pumpable homogeneous liquids from a few purpose-built plants to supply worldwide clean jet/diesel fuel needs. Since certain process streams herein can also be used for detergents, the invention has the potential to make all manner of cleaning compositions, especially surfactants, using compounds from these streams more affordable for the consumer.
The new processes herein are simple and can use known process units, with a need only to connect or configure them in the novel ways taught herein. The processes thus require a minimum of additional new process development and are very practical. Unexpected process unit combinations herein include piggyback cracking (based on very old detergent art) on processes having modern hydrocracking/hydroisomerization (based on recent lubricant-making art, see for example S. J. Miller, Microporous Materials, Vol. 2 (1994), pp. 439-449.
The processes of the present invention utilize what are potentially the best and largest commercial sources of mid-chain methyl-branched paraffins worldwide, and flexibly accommodate the use of leading-edge technologies for making the main stream. There is little or no waste, since all byproducts from the side-stream(s) can be used or returned to the main stream of the fuel plant at a value equal or greater than on receipt.
Preferred embodiments of the process, which include FISCHER TROPSCH paraffin making in the main stream of the fuel plant, have an Oxo reaction, which can use substantially the same synthesis gas or H2/CO ratio as the FISCHER TROPSCH paraffin making. The compositions produced have numerous advantages. The products of the present processes are unexpectedly superior for improving low temperature properties and fuel lubricity, permitting clean (low sulfur, low nitrogen) fuels yet having them be effective in the lubrication of fuel injectors and pumps. The nonlinear alcohol derivatives in the present compositions indeed have excellent surface properties at metal surfaces of components of internal combustion engines, especially in frictionally affected situations.
Most importantly, the specific long-chain branched primary Oxo alcohol derivatives produced herein have excellent low-temperature properties and significant lubricity-enhancing power for jet, diesel and turbine fuels. This is very important in view of various technological and environmental pressures to remove the inherent sulfur-based, nitrogen-based and aromatic based lubricity improvers from such fuels.
Moreover the present long-chain branched primary Oxo alcohol derivatives are especially useful for use in new, cleaner, small diesel engines being developed for use in automobiles. Thus, not only in its process embodiments, but also in its composition and method of use embodiments as described below, the present invention has high and significant value.
These and other aspects, features and advantages will be apparent from the following description and the appended claims. All parts, percentages and ratios used herein are expressed as percent weight unless otherwise specified. All documents cited are, in relevant part, incorporated herein by reference.